Re: recent troubles with float vectors & bitwise ops

[Paul Brook <paul at codesourcery dot com>]

On Friday 24 August 2007, Ian Lance Taylor wrote:
> Paolo Bonzini <paolo.bonzini@lu.unisi.ch> writes:
> > 1) neg, abs and copysign operations on vectors.  These we can make
> > available via builtins (for - of course you don't need it); we already
> > support them in many back-ends.
>
> Here is my point of view.  People using the vector extensions are
> already writing inherently machine specific code, and they are
> (ideally) familiar with the instruction set of their processor.

By the same argument, If you're already writing machine specific code then 
there shouldn't be a problem using machine specific intrinsics. I admit I've 
never been convinced that the generic vector support was sufficient to write 
useful code without resorting to machine specific intrinsics.

> Permitting this extension continues the preexisting behaviour, and it
> helps programmers and helps existing code. ?Who does it hurt to permit
> this extension? ?Who does it help to forbid this extension?

I'm partly worried about cross-platform compatibility, and what this imples 
for other SIMD targets.
At minimum we need to fix the internals documentation to say how to support 
this extension. The current docs are unclear whether (or:V2SF ...) is valid 
RTL.

Paul